The methods and systems presented below are related, in general, to electrical power transfer devices. The methods and systems presented below are related, in particular, to electrical power transfer devices wherein pulse width modulation is used.
When used in electrical power transfer devices, pulse width modulation is a technique whereby various aspects of electrical power transfer devices are controlled. Typically, in pulse width modulation, a DC power source capable of producing at least two different discrete voltage levels (e.g., a xe2x80x9chighxe2x80x9d voltage level such as five volts, and a xe2x80x9clowxe2x80x9d voltage level such as zero volts) is utilized such that the time during which the voltage is high controls a particular power transfer device. For example, the time during which the voltage is high can be used to control a DC motor by driving the DC motor with short pulses. The longer the pulses, the faster the motor turns, and vice versa.
Graphically, the output of the voltage source over time will look like a train of pulses, where the widths of pulses in the train are varied such that effective control of the power transfer device takes place. Accordingly, insofar as modulation is generally defined as a regulating according to measure or proportion, and since the widths of various electric pulses in the train are being varied to ensure that some aspect of the power transfer device is being effectively controlled, controlling the widths of the various pulses to ensure that some aspect of the power transfer device is being effectively controlled is often referred to as xe2x80x9cpulse width modulation.xe2x80x9d
Insofar as pulse modulation schemes modulate pulse widths in order to control devices, a pulse modulation scheme needs an unmodulated train of pulses whose widths can be varied. The common way in which such an unmodulated train of pulses is produced within the related art is to use a standard digital clock circuit as the source of the unmodulated pulse train. A standard digital clock circuit produces a high voltage-low voltage alternating waveform of a prespecified period. Accordingly, it is possible to use a standard digital clock circuit to produce a pulse width modulated signal having a positive moving pulse width between a value greater than zero and less than one part of the period of the clock signal. The related art recognizes the foregoing scheme as the method of choice for generating pulse width modulated control signals. In addition, although the preceding discussion described generation of pulse width modulated signals via the use of a clock signal, those having ordinary skill in the art will appreciate that other pulse width modulation schemes likewise exhibit strong fundamental frequency characteristics, even though such pulse width modulation schemes might not directly use a clock signal.
In one embodiment, a method for use with a power transfer device is characterized by shifting a control signal with a waveform having a randomly variable period; and switching the power transfer device with a resultant shifted control signal.
In another embodiment of the method, the power transfer device is characterized by: a DC-to-AC converter, a DC-to-DC pulse width modulated converter, a DC-to-transformer tank circuit controller, a DC-to-wave generating controller, a DC-to-AC power converter, or an AC-to-AC power flow controller.
In another embodiment of the method, shifting a control signal with a waveform having a randomly variable period is characterized by: introducing at least one random timing variation into a fixed-frequency periodic control signal.
In another embodiment of the method, shifting a control signal with a waveform having a randomly variable period is characterized by: shifting one or more individual pulses in response to at least one substantially instantaneous magnitude selected out from a random noise reference.
In another embodiment of the method, shifting one or more individual pulses in response to at least one substantially instantaneous magnitude selected out from a random noise reference is characterized by: prespecifying an upper limit timing variation and a lower limit timing variation for each successive time delay.
In another embodiment of the method, shifting one or more individual pulses in response to at least one substantially instantaneous magnitude selected out from a random noise reference is characterized by: screening at least one pulse from the control signal to obtain the one or more individual pulses.
In another embodiment of the method, shifting one or more individual pulses in response to at least one substantially instantaneous magnitude selected out from a random noise reference is characterized by: shifting an upward edge of an individual pulse; shifting a downward edge of the individual pulse; and constructing a quasi-time-shifted version of the individual pulse from the shifted upward edge and shifted downward edge of the individual pulse.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: controlling a wave-shaping device with the control signal.
In another embodiment of the method, controlling a wave-shaping device with the shifted control signal is characterized by: controlling a wave-shaping device in an uninterruptible power system, or a wave-shaping device in a variable frequency motor controller, or a wave-shaping device in a DC-to-AC power conversion system used to feed an AC power utility grid.
In another embodiment of the method, the wave-shaping device is a related-art wave-shaping device that is otherwise controlled with the unshifted control signal, whereby the method is substantially backwards compatible with the related-art wave-shaping device.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: controlling a wave-shaping device with the shifted control signal, thus allowing operation of the wave-shaping device at an average frequency within the audio range but without a fixed audio frequency signal.
In another embodiment of the method, the power transfer device is a related-art power transfer device that is otherwise switched with the unshifted control signal, whereby the method is substantially backwards compatible with the related-art power transfer device.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: switching said power transfer device with the shifted control signal, thus allowing operation of said power transfer device at an average frequency within the audio range but without a fixed audio frequency signal.
In another embodiment of the method, shifting a control signal with a waveform having a randomly variable period is characterized by: generating a series of random numbers; obtaining timing information from the control signal in a digital format; shifting the obtained timing information by using the series of random numbers to calculate a timing shift from each random number to result in shifted timing information; transforming the shifted timing information to establish a digital-format resultant shifted control signal; and establishing the resultant shifted control signal from the digital-format resultant shifted control signal.
In another embodiment of the method, generating a series of random numbers is characterized by: selecting at least one digital bit from a stored group of digital bits in order to simulate the results desired from a series of random numbers.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: controlling a wave-shaping device with the shifted control signal.
In another embodiment of the method, controlling a wave-shaping device with the shifted control signal is characterized by: controlling a wave-shaping device in an uninterruptible power system, or a wave-shaping device in a variable frequency motor controller, or a wave-shaping device in a DC-to-AC power conversion system used to feed an AC power utility grid.
In another embodiment of the method, the wave-shaping device is a related-art wave-shaping device that is otherwise controlled with the unshifted control signal, whereby the method is substantially backwards compatible with the related-art wave-shaping device.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: controlling a wave-shaping device with the shifted control signal, thus allowing operation of the wave-shaping device at an average frequency within the audio range but without a fixed audio frequency signal.
In another embodiment of the method, the power transfer device is a related-art power transfer device that is otherwise switched with the unshifted control signal, whereby the method is substantially backwards compatible with the related-art power transfer device.
In another embodiment of the method, switching the power transfer device with a resultant shifted control signal is characterized by: switching the power transfer device with the shifted control signal, thus allowing operation of the power transfer device at an average frequency within the audio range but without a fixed audio frequency signal.
In addition to the foregoing, other method embodiments are described in the claims, drawings, and text forming a part of the present application.
In one or more various embodiments, related systems include but are not limited to circuitry and/or programming for effecting the foregoing-referenced method embodiments; the circuitry and/or programming can be virtually any combination of hardware, software, and/or firmware configured to effect the foregoing-referenced method embodiments depending upon the design choices of the system designer.
In addition to the foregoing, other system embodiments are described in the claims, drawings, and text forming a part of the present application.
The foregoing is a summary and thus contains, by necessity; simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is NOT intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth herein.